Photoresists are commonly used in photolithography processes during fabrication of semiconductor devices comprising integrated circuits (IC). In the fabrication processes, photoresists are also used for patterning. Photoresist patterning includes process steps such as photoresist coating, softbaking, mask aligning, pattern exposing, photoresist development, and hard baking. Photoresists are eventually removed through dry or wet etching, stripping and/or other cleaning processes.
Any photoresist residues remaining on the semiconductor device will affect the quality of subsequent processing steps, and may even damage structures of semiconductor devices. Meanwhile, as sizes of active circuit elements in ICs continues to decrease, with corresponding increases in the pattern densities of circuits in these ICs, quality of each processing step and resulting features of devices should be precisely controlled.
Via holes are through holes made in a substrate, for different purposes. For example, via holes are used to connect circuit patterns in adjacent metal layers, or to ground semiconductor devices and passive devices. Via holes are made through dielectric layers, for subsequent metal deposition to form a plug and create interconnect between two metal lines in different layers. Multi-level interconnect schemes employ such via holes in large numbers. Processes used to perform such interconnection using via holes include the single damascene process and the dual-damascene process.